1. Field of the Invention
The invention relates to a hand-held power tool, in particular an impact driver, an impact drill, or a rotary hammer, having at least one drive unit and/or output. The drive unit and/or output has at least one line of action, which is defined in a rotary hammer, for example, by the axial action direction of an impact mechanism. At least along this line of action, the drive unit and/or output produces oscillations, which can be transmitted in the form of vibrations to a housing and/or handle of the power tool. Users of the power tool find these vibrations unpleasant. In order to reduce these oscillations/vibrations, the power tool is equipped with at least one vibration absorber unit.
2. Description of the Prior Art
A variety of hand-held power tools with vibration absorber units for reducing oscillation are already known. Among others, EP 1 252 976 A1 has disclosed a vibration absorber unit, which, when used in hand-held power tools operated in a hammering mode such as rotary and/or chisel hammers, exerts a damping action on vibrations that propagate along a main oscillation axis extending parallel to the line of action of an impact mechanism. To this end, EP 1 252 976 A1 uses a so-called inertial vibration absorber that has a vibration absorbing element, which is supported so that it is able to move in an axial direction parallel to the line of action of the impact mechanism between two return springs. In this case, the vibration absorbing element is embodied as a mass element, also referred to as a vibration absorbing mass. By means of this arrangement, the vibration absorbing element functions as a counter-oscillator, which is displaced from a rest position by the oscillations propagating along the line of action and follows the oscillations in a delayed fashion due to its inertia. The return springs in turn damp the displacements of the vibration absorbing element, thus drawing energy from the oscillations. Because of their embodiment as a mass/spring system, vibration absorber units of this kind preferably act on a narrowly delimited frequency spectrum.
In addition, EP 1 439 038 A1 and EP 1 464 449 A2 among others have disclosed vibration absorbing systems that are actuated by different driving mechanisms. In these arrangements, the driving mechanisms couple the axially mobile vibration absorbing element to the drive unit and/or output producing the oscillations. These vibration absorbing systems, however, are also situated so that the vibration absorbing element moves axially along an axis parallel to the line of action of the drive unit and/or output.
In hand-held power tools, which in addition to an impact drive, also have a rotary drive for the tool, vibrations do not occur only in the axial direction, i.e. parallel to the line of action of the impact mechanism. In particular, rotatory vibrations occur due to the recoiling of a tool that is driven at least in rotary fashion during the machining of a work piece. In addition, in hand-held power tools in which the center of mass is situated far away from a tool axis, tilting moments occur, which excite vibrations transverse to the impact direction.